4.6 Circle properties

Recognise the centre, radius, chord, diameter, circumference, tangent, arc, sector and segment of a circle.

understand chord and tangent properties of circles Two tangents from a point to a circle are equal in length Tangents are perpendicular to the radius at the point of contact The line from the centre of a circle which is perpendicular to a chord bisects the chord (and the converse)

understand and use the internal and external intersecting chord properties

recognise the term ‘cyclic quadrilateral’

understand and use angle properties of the circle including: (i) angle subtended by an arc at the centre of a circle is twice the angle subtended at any point on the remaining part of the circumference (ii) angle subtended at the circumference by a diameter is a right angle (iii) angles in the same segment are equal (iv) the sum of the opposite angles of a cyclic quadrilateral is 180° (v) the alternate segment theorem Formal proof of these theorems is not required